Radar Data Analyses for a Single Rainfall Event and Their Application for Flow Simulation in an Urban Catchment Using the SWMM Model

Abstract

The disadvantage of radar measurements is that the obtained rainfall data is imprecise. Therefore, the use of radar data in hydrological applications usually requires correction. The main aim of the study was to verify and optimize various methods of estimating the rainfall depths for single events based on radar data, as well as determining their influence on the values of peak flow and outflow volume of hydrographs simulated using the SWMM (Storm Water Management Model) hydrodynamic model. Regression analyses were used to find a relationship between the rain gauge rainfall rate R and radar reflectivity Z for the urban catchment of the Służewiecki Stream in Warsaw, Poland. Five methods for determining calculational values of radar reflectivity in reference to specific rainfall cells with 1 km resolution within an event duration were applied. Moreover, the correction coefficient for data from the SRI (Surface Rainfall Intensity) product was established. The Z-R relationships determined in this study offer much better rainfall rate estimation as compared to Marshall-Palmer’s relationship. Different scenarios were applied to investigate the stream response to changes in rainfall depths estimated on the basis of radar data, in which the data both for 2 existing, as well as 64 virtual, rain gauges assigned to appropriate rainfall cells in the catchment were included. Relatively good agreement was achieved between the measured parameters of the hydrograph of flows and those simulated in response to rainfall depths which had been calculated for single events using the correction coefficient and the determined Z-R relationships. Radar estimates of rainfall depths based on the tested methods can be used as input data to the SWMM model for the purpose of simulating flows in the investigated urban catchment.

Evaluation of the Impact of Rainfall Inputs on Urban Rainfall Models: A Systematic Review

“…Rainfall data obtained via this method are the most commonly used rainfall data for rainfall input to urban flood models. However, this method has serious difficulties, including high station construction cost and low spatial resolution [17]. The other method is new technology measurement, mainly through radar, remote sensing, microwave, and numerical weather forecasting.…”

“…Resolution seeks to improve the accuracy of simulated predictions of urban rain flood models [60,61]; this is likely to remain a developing trend in precipitation measurement. However, the observation accuracy of this method is not enough, and it usually needs to be corrected in conjunction with surface rain measurement [17]. In addition, the observation data usually need to be downscaled and inferred to be applied; this technology is very complex.…”

“…Water 2020, 12, x FOR PEER REVIEW 14 of 20 accuracy of this method is not enough, and it usually needs to be corrected in conjunction with surface rain measurement [17]. In addition, the observation data usually need to be downscaled and inferred to be applied; this technology is very complex.…”

“…This study also systematically reviews the research and model development [16] work regarding recent urban rain flood models. Rainfall observation from rainfall stations has the advantage of high observation accuracy, but the spatiotemporal effect is poor [17]. New technology of rainfall measurement is designed to improve the spatial and temporal resolution of rainfall input to the model, but its observation accuracy is far from sufficient [18].…”

Przestrzenne i sezonowe zróżnicowanie wybranych parametrów jakości wody w zlewni zurbanizowanej na przykładzie Potoku Służewieckiego = Spatial and seasonal variability of selected water-quality parameters in an urbanised catchment as exemplified by Warsaw’s Służewiecki Stream

“…W ciągu ostatnich kilkunastu lat ciek ten stał się ważnym obiektem badań prowadzonych zarówno przez ośrodki naukowo-badawcze, jak i instytucje ochrony środowiska. Najwięcej uwagi poświęcono przepływom wezbraniowym Potoku (Oksiuta, 2007;Krajewski i Banasik, 2013;Barszcz, 2017), metodom ich prognozowania (Barszcz, 2009(Barszcz, , 2014b(Barszcz, , 2015(Barszcz, , 2018, jak również wykorzystaniu obiektów małej retencji do redukcji fal kulminacyjnych (Pietrak i Banasik, 2009;Barszcz, 2014a). W związku z intensywną, postępującą zabudową zlewni Potoku Służewieckiego, analizie poddano również wpływ zmian użytkowania terenu na obieg wody w jej obrębie (Oksiuta, 2008).…”